Air-conditioning apparatus

ABSTRACT

In an air-conditioning apparatus, a heat source side heat exchanger  12,  intermediate heat exchangers  15   a  and  15   b,  and use side heat exchangers  26   a  to  26   d  are separately formed and adapted to be disposed at separate locations, respectively. There are provided a defrosting operation function to melt frost attached around the heat source side heat exchanger  12,  and a heating function during defrosting operation that drives a pump  21   a  to circulate a heat medium and supply heating energy to the use side heat exchangers  26   a  to  26   d  in need of heating to perform heating operation. The defrosting operation function can be executed by switching a four-way valve  11  to cooling side to introduce a high-temperature high-pressure refrigerant flowed out of the compressor  10  into the heat source side heat exchanger  12.

TECHNICAL FIELD

The present invention relates to an air-conditioning apparatus such as amultiple air conditioner for buildings.

BACKGROUND ART

In a multiple air conditioner, which is a conventional air-conditioningapparatus, cooling energy or heating energy is delivered indoors bycirculating a refrigerant between an outdoor unit, which is a heatsource apparatus installed outdoors, and an indoor unit installedindoors. As for the refrigerant, an HFC (hydrofluorocarbon) refrigerantis mainly used and the air-conditioning apparatus using a naturalrefrigerant such as CO₂ is proposed.

In a chiller, which is another conventional air-conditioning apparatus,cooling energy or heating energy is generated in a heat source apparatusdisposed outdoors, cooling energy or heating energy is transferred to aheat medium such as water and an anti-freezing liquid at a heatexchanger disposed in an outdoor unit, and cooling operation or heatingoperation is performed by carrying the heat medium to a fan coil unit, apanel heater and the like, which are of an indoor unit (Refer to PatentLiterature 1, for example).

-   Patent Literature 1: Japanese Unexamined Patent Application    Publication No. 2003-343936

SUMMARY OF INVENTION Technical Problem

In the conventional air-conditioning apparatus, since a refrigerant iscirculated directly in an indoor unit, heating energy can be supplied tothe indoor unit during defrosting operation, causing to lower the roomtemperature while defrosting. Further, since no heating operation ispossible while defrosting, system efficiency is lowered includingdefrosting. A chiller performs heat exchange between the refrigerant andwater outdoors to convey water, therefore, carrying power of water isextremely large, and even when heating energy can be supplied duringdefrosting operation, the system efficiency including defrosting isdeteriorated because of a large amount of carrying power of the pump,causing a problem of non-energy saving.

The present invention is made to solve the above-mentioned problems andits object is to obtain an air-conditioning apparatus capable ofsuppressing the lowering of the indoor temperature and reducing powernecessary for circulating a secondary heat medium by circulating thesecondary heat medium in the indoor unit during defrosting operation.

Solution to Problem

The air-conditioning apparatus according to the present inventionincludes:

intermediate heat exchangers for heating and cooling a heat medium thatexchanges heat between a refrigerant and the heat medium different fromthe refrigerant;

a refrigeration cycle in which a compressor, a four-way valve thatswitches the outlet-side flow path of the compressor between at heatingoperation and at cooling operation, a heat source side heat exchanger,at least one expansion valve and a refrigerant-side flow paths of theintermediate heat exchanger are connected via piping through which therefrigerant flows, and

a heat medium circulation circuit in which a heat medium side flow pathof the intermediate heat exchanger, a pump, and a use side heatexchanger are connected via piping through which the heat medium flows.

The heat source side heat exchanger, the intermediate heat exchangers,and the use side heat exchanger are separately formed respectively andadapted to be disposed at separate locations from each other.

The air-conditioning apparatus is provided with a defrosting operationfunction to melt frost attached around the heat source side heatexchanger, and a heating function during defrosting operation thatdrives the pump to circulate the heat medium while operating thedefrosting operation function and supply heating energy to the use sideheat exchanger in need of heating to perform heating operation.

The defrosting operation function can be executed by switching thefour-way valve to the cooling side to introduce a high-temperaturehigh-pressure refrigerant into the heat source side heat exchanger.

Advantageous Effects of Invention

In the air-conditioning apparatus according to the present invention,since a refrigeration cycle having a heat source side heat exchanger anda heat medium circulation circuit supplying heating energy to a use sideheat exchanger are separated, heating energy can be continuouslysupplied for a certain period so as to heat indoors even when beingswitched from heating operation to defrosting operation. The heat sourceside heat exchanger, the intermediate heat exchangers, and the use sideheat exchanger are separately formed respectively, and are adapted to bedisposed at separate locations from each other, therefore, carryingpower of the heat medium can be made small, and system efficiencyincluding defrosting being improved to contribute to energy saving.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an entire constitution diagram of an air-conditioningapparatus according to Embodiment 1 of the present invention.

FIG. 2 is another entire constitution diagram of the air-conditioningapparatus according to Embodiment 1 of the present invention.

FIG. 3 is a circuit diagram for a refrigerant and a heat medium of theair-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 4 is a circuit diagram showing the refrigerant and the heat mediumflows at the time of cooling only operation.

FIG. 5 is a circuit diagram showing the refrigerant and the heat mediumflows at the time of heating only operation.

FIG. 6 is a circuit diagram showing the refrigerant and the heat mediumflows at the time of cooling-main operation.

FIG. 7 is a circuit diagram showing the refrigerant and the heat mediumflows at the time of heating-main operation.

FIG. 8 is a circuit diagram showing the refrigerant and the heat mediumflows at the time of defrosting operation.

FIG. 9 is a flow chart illustrating flow amount control operation of theheat medium by a controller of the air-conditioning apparatus.

FIG. 10 is a circuit diagram for the refrigerant and the heat medium ofthe air-conditioning apparatus according to Embodiment 2 of the presentinvention.

-   1 heat source apparatus (outdoor unit)-   2 indoor unit-   3 relay unit-   3 a main relay unit-   3 b(1), 3 b(2) sub relay unit-   4 refrigerant pipeline-   5 heat medium pipeline-   6 outdoor space-   7 indoor space-   8 non-air conditioned space-   9 structures such as building-   10 compressor-   11 four-way valve-   12 heat source side heat exchanger-   13 a, 13 b, 13 c, 13 d check valve-   14 gas-liquid separator-   15 a, 15 b intermediate heat exchanger-   16 a, 16 b, 16 c, a6 d, 16 e expansion valve-   17 accumulator-   21 a, 21 b pump-   22 a, 22 b, 22 c, 22 d flow path switching valve-   23 a, 23 b, 23 c, 23 d flow path switching valve-   24 a, 24 b, 24 c stop valve-   25 a, 25 b, 25 c, 25 d flow amount adjustment valve-   26 a, 26 b, 26 c, 26 d use side heat exchanger-   27 a, 27 b, 27 c, 27 d bypass-   31 a, 31 b first temperature sensor-   32 a, 32 b second temperature sensor-   33 a, 33 b, 33 c, 33 d third temperature sensor-   34 a, 34 b, 34 c, 34 d fourth temperature sensor-   35 fifth temperature sensor-   36 pressure sensor-   37 sixth temperature sensor-   38 seventh temperature sensor

Description of Embodiments

Detailed descriptions will be given to embodiments of the presentinvention.

Embodiment 1

FIGS. 1 and 2 are an entire constitution diagram of an air-conditioningapparatus according to Embodiment 1 of the present invention. Theair-conditioning apparatus includes a heat source apparatus (outdoorunit) 1, an indoor unit 2 subjected to air conditioning of indoors, anda relay unit 3 that is separated from the outdoor unit 1 to be disposedin a non-air conditioned space 8. The heat source apparatus 1 and therelay unit 3 are connected by refrigerant pipeline 4 and a refrigerant(a primary medium) flows therein. The relay unit 3 and the indoor unit 2are connected by heat medium pipeline 5 and a heat medium (a secondarymedium) such as water and an anti-freezing liquid flows therein. Therelay unit 3 performs heat exchange between the refrigerant sent fromthe heat source apparatus 1 and the heat medium sent from the indoorunit 2.

The heat source apparatus 1 is usually disposed in an outdoor space 6,which is an external space of structures such as building 9. The indoorunit 2 is disposed at a position capable of carrying heated or cooledair to an indoor space 7 such as a living room inside of structures suchas building 9. The relay unit 3 is housed in a different housing fromthe heat source apparatus 1 and the indoor unit 2, being connected bythe refrigerant pipeline 4 and the heat medium pipeline 5, and beingadapted to be capable of being disposed at a different location from theoutdoor space 6 and the indoor space 7. In FIG. 1, the relay unit 3 isinside the building 9, however, being disposed in a non-air conditionedspace 8 such as under the roof, which is a different space from theindoor space 7. The relay unit 3 can be disposed in a place such as acommon use space having an elevator or the like.

The heat source apparatus 1 and the relay unit 3 are configured so as tobe connected using two refrigerant pipelines 4. The relay unit 3 andeach indoor unit 2 are connected using two heat medium pipelines 5respectively. Connection using two pipes facilitates the construction ofthe air-conditioning apparatus.

FIG. 2 shows a case where a plurality of relay units 3 are provided.That is, the relay unit 3 is divided into one main relay unit 3 a andtwo sub relay units 3 b(1) and 3 b(2) derived therefrom. Accordingly, aplurality of sub relay units 3 b can be connected with one main relayunit 3 a. In this configuration, there are three connection pipelinesbetween the main relay unit 3 a and the sub relay units 3 b.

In FIGS. 1 and 2, the indoor unit 2 is shown with a ceiling cassettetype being an example, however, it is not limited thereto. Any type suchas a ceiling-concealed type and a ceiling-suspended type will beallowable as long as heated or cooled air can be blown out into theindoor space 7 directly or through a duct or the like.

The heat source apparatus 1 is explained with the case of being disposedin the outdoor space 6 outside the building 9 as an example, however, itis not limited thereto. For example, the heat source apparatus 1 may bedisposed in a surrounded space like a machine room near a ventilatingopening. The heat source apparatus 1 may be disposed inside the building9 to discharge exhaust heat to outside of the building 9 through anexhaust duct. A water-cooled type heat source apparatus may be employedto be disposed in the building 9.

The relay unit 3 may be disposed near the heat source apparatus 1, whichmay be against energy saving.

Next, descriptions will be given to detailed configuration of the aboveair-conditioning apparatus. FIG. 3 is a circuit diagram for therefrigerant and the heat medium of the air-conditioning apparatusaccording to Embodiment 1 of the present invention. The air-conditioningapparatus, as shown in FIG. 3, has a heat source apparatus 1, an indoorunit 2, and a relay unit 3.

The heat source apparatus 1 includes a compressor 10, a four-way valve11, a heat source side heat exchanger 12, check valves 13 a, 13 b, 13 cand 13 d, and an accumulator 17. The indoor unit 2 includes use sideheat exchangers 26 a to 26 d. The relay unit 3 includes a main relayunit 3 a and a sub relay unit 3 b. The main relay unit 3 a includes agas-liquid separator 14 to separate a gas phase and a liquid phase ofthe refrigerant and an expansion valve 16 e (an electronic expansionvalve, for example).

The sub relay unit 3 b includes intermediate heat exchangers 15 a and 15b, expansion valves (electronic expansion valves, for example) 16 a to16 d, pumps 21 a and 21 b, and flow path switching valves 22 a to 22 dand 23 a to 23 d such as a three-way valve. The flow path switchingvalves are installed at inlet side flow paths and outlet side flow pathsof each use side heat exchanger 26 a to 26 d, correspondingly. The flowpath switching valves 22 a to 22 d switch outlet side flow paths amongplurally disposed intermediate heat exchangers. The flow path switchingvalves 23 a to 23 d switch inlet side flow paths among them. In thisexample, the flow path switching valves 22 a to 22 d perform operationsto switch outlet side flow paths between the intermediate heatexchangers 15 a and 15 b, and the flow path switching valves 23 a to 23d perform operations to switch inlet side flow paths between theintermediate heat exchangers 15 a and 15 b.

At inlet sides of use side heat exchangers 26 a to 26 d, stop valves 24a to 24 d for opening and closing flow paths are provided, and at outletsides thereof, flow amount adjustment valves 25 a to 25 d for adjustingflow amount are provided, respectively. The inlet side flow path and theoutlet side flow path of each use side heat exchanger 26 a to 26 d areconnected by bypasses 27 a to 27 d via flow amount adjustment valves 25a to 25 d.

The sub relay unit 3 b includes temperature sensors and pressure sensorsas follows:

-   the temperature sensors (first temperature sensors) 31 a and 31 b to    detect the outlet temperature of the heat medium of the intermediate    heat exchangers 15 a and 15 b;-   the temperature sensors (second temperature sensors) 32 a and 32 b    to detect the inlet temperature of the heat medium of the    intermediate heat exchangers 15 a and 15 b;-   the temperature sensors (third temperature sensors) 33 a to 33 d to    detect the inlet temperature of the heat medium of the use side heat    exchangers 26 a to 26 d;-   the temperature sensors (fourth temperature sensors) 34 a to 34 d to    detect the outlet temperature of the heat medium of the use side    heat exchangers 26 a to 26 d;-   the temperature sensor (a fifth temperature sensor) 35 to detect the    refrigerant outlet temperature of the intermediate heat exchanger 15    a;-   the pressure sensor 36 to detect the refrigerant outlet pressure of    the intermediate heat exchanger 15 a;-   the temperature sensor (a sixth temperature sensor) 37 to detect the    refrigerant inlet temperature of the intermediate heat exchanger 15    b; and-   the temperature sensor (a seventh temperature sensor) 38 to detect    the refrigerant outlet temperature of the intermediate heat    exchanger 15 b.

These temperature sensors and pressure sensors can employ a variety ofthermometers, temperature sensors, pressure gauge, and pressure sensors.

The compressor 10, the four-way valve 11, the heat source side heatexchanger 12, the check valves 13 a, 13 b, 13 c and 13 d, the gas-liquidseparator 14, the expansion valves 16 a to 16 e, the intermediate heatexchangers 15 a and 15 b, and the accumulator 17 configure arefrigeration cycle.

The intermediate heat exchanger 15 a, the pump 21 a, the flow pathswitching valves 22 a to 22 d, the stop valves 24 a to 24 d, the useside heat exchangers 26 a to 26 d, the flow amount adjustment valves 25a to 25 d, and the flow path switching valves 23 a to 23 d configure aheat medium circulation circuit. In the same way, the intermediate heatexchanger 15 b, the pump 21 b, the flow path switching valves 22 a to 22d, the stop valves 24 a to 24 d, the use side heat exchangers 26 a to 26d, the flow amount adjustment valves 25 a to 25 d, and the flow pathswitching valves 23 a to 23 d configure a heat medium circulationcircuit.

As shown in figures, each of use side heat exchangers 26 a to 26 d isprovided with the intermediate heat exchangers 15 a and 15 b in parallelin plural, each configuring the heat medium circulation circuit.

In the heat source apparatus 1, a controller 100 is provided thatcontrols equipment constituting thereof to make the heat sourceapparatus 1 to perform operations as what is called an outdoor unit. Inthe relay unit 3, a controller 300 is provided that controls equipmentconstituting thereof and has means to perform functions and operationsto be mentioned later. These controllers 100 and 300 are composed ofsuch as microcomputers to be communicably connected with each other.Next, operations of each operation mode of the above air-conditioningapparatus will be explained.

<Cooling Only Operation>

FIG. 4 is a circuit diagram showing a refrigerant and a heat mediumflows at the time of cooling only operation. In the cooling onlyoperation, the refrigerant is compressed by the compressor 10, turnedinto a high-temperature high-pressure gas refrigerant to enter the heatsource side heat exchanger 12 via the four-way valve 11. The refrigerantis condensed and liquefied there, passes through the check valve 13 a,and flowed out of the heat source apparatus 1 into the relay unit 3 viathe refrigerant pipeline 4. In the relay unit 3, the refrigerant entersthe gas-liquid separator 14 to be guided into the intermediate heatexchanger 15 b via the expansion valves 16 e and 16 a. Thereby, therefrigerant is expanded by the expansion valve 16 a to turn into alow-temperature low-pressure two-phase refrigerant and the intermediateheat exchanger 15 b operates as an evaporator. The refrigerant turnsinto a low-temperature low-pressure gas refrigerant in the intermediateheat exchanger 15 b and flows out of the relay unit 3 via the expansionvalve 16 c to flow into the heat source apparatus 1 again via therefrigerant pipeline 4. In the heat source apparatus 1, the refrigerantpasses through the check valve 13 d to be sucked into the compressor 10via the four-way valve 11 and the accumulator 17. Then, the expansionvalves 16 b and 16 d have an opening-degree small enough for therefrigerant not to flow and the expansion valve 16 c is made to be afull-open state so as not to cause a pressure loss.

Next, descriptions will be given to movement of the secondary side heatmedium (water, anti-freezing liquid, etc.) In intermediate heatexchanger 15 b, cooling energy of the refrigerant on the primary side istransferred to the heat medium on the secondary side, and the cooledheat medium is made to flow in the secondary side piping by the pump 21b. The heat medium flowed out of the pump 21 b passes through the stopvalves 24 a to 24 d via the flow path switching valves 22 a to 22 d toflow into the use side heat exchangers 26 a to 26 d and the flow amountadjustment valves 25 a to 25 d. Then, through the operation of the flowamount adjustment valves 25 a to 25 d, only the heat medium having aflow amount necessary to cover the air-conditioning load requiredindoors is made to flow into the use side heat exchangers 26 a to 26 d,and the remaining passes through the bypasses 27 a to 27 d to make nocontribution to heat exchange. The heat medium passing through thebypasses 27 a to 27 d merges with the heat medium passing through theuse side heat exchangers 26 a to 26 d, passes through the flow pathswitching valves 23 a to 23 d, and flows into the intermediate heatexchanger 15 b to be sucked again into the pump 21 b. Theair-conditioning load required indoors can be covered by controlling adifference between the detection temperatures of the third temperaturesensors 33 a to 33 d and the fourth temperature sensors 34 a to 34 d tomaintain a predetermined target value.

Since there is no need to flow the heat medium to the use side heatexchanger (including thermo-off) having no air-conditioning load, theflow path is closed by the stop valves 24 a to 24 d and the heat mediumis made not to flow into the use side heat exchanger. In FIG. 4, whilein the use side heat exchangers 26 a and 26 b, the heat medium is madeto flow because of an air-conditioning load, in the use side heatexchangers 26 c and 26 d, there is no air-conditioning load andcorresponding stop valves 24 c and 24 d are closed.

<Heating Only Operation>

FIG. 5 is a circuit diagram showing a refrigerant and a heat mediumflows at the time of heating only operation. In the heating onlyoperation, the refrigerant is compressed by the compressor 10, turnsinto a high-temperature high-pressure gas refrigerant, passes throughthe check valve 13 b via the four-way valve 11, and flows out of theheat source apparatus 1 via the check valve 13 b to flow into the relayunit 3 via the refrigerant pipeline 4. In the relay unit 3, therefrigerant is guided into the intermediate heat exchanger 15 a throughthe gas-liquid separator 14, condensed and liquefied in the intermediateheat exchanger 15 a to flow out of the relay unit 3 through theexpansion valves 16 d and 16 b. Thereby, the refrigerant is expanded bythe expansion valve 16 b, turned into a low-temperature low-pressuretwo-phase refrigerant, and flows into the heat source apparatus 1 againthrough the refrigerant pipeline 4. In the heat source apparatus 1, therefrigerant is guided into the heat source side heat exchanger 12through the check valve 13 c and the heat source side heat exchanger 12operates as an evaporator. The refrigerant turns into a low-temperaturelow-pressure gas refrigerant there to be sucked into the compressor 10via the four-way valve 11 and the accumulator 17. Thereby, the expansionvalve 16 e and the expansion valve 16 a or 16 c are made to have a smallopening-degree so that no refrigerant flows therethrough.

Next, movement of the secondary side heat medium (water, anti-freezingliquid, etc.) will be explained. In the intermediate heat exchanger 15a, heating energy of the primary side refrigerant is transferred to thesecondary side heat medium and the heated heat medium is made to flow inthe secondary side piping by the pump 21 a. The heat medium flowed outof the pump 21 a passes through the stop valves 24 a to 24 d via theflow path switching valves 22 a to 22 d to flow into the use side heatexchangers 26 a to 26 d and the flow amount adjustment valves 25 a to 25d. Then, through the operation of the flow amount adjustment valves 25 ato 25 d, only the heat medium having a flow amount necessary to coverthe air-conditioning load required indoors is made to flow into the useside heat exchangers 26 a to 26 d, and the remaining passes through thebypasses 27 a to 27 d to make no contribution to heat exchange. The heatmedium passing through the bypasses 27 a to 27 d merges with the heatmedium passing through the use side heat exchangers 26 a to 26 d, passesthrough the flow path switching valves 23 a to 23 d, and flows into theintermediate heat exchanger 15 a to be sucked again into the pump 21 a.The air-conditioning load required indoors can be covered by controllinga difference between the detection temperatures of the third temperaturesensors 33 a to 33 d. and the fourth temperature sensors 34 a to 34 d tomaintain a target value.

Since there is no need to flow the heat medium to the use side heatexchanger (including thermo-off) having no air-conditioning load, theflow path is closed by the stop valves 24 a to 24 d. and the heat mediumis made not to flow into the use side heat exchanger. In FIG. 5, whilein the use side heat exchangers 26 a and 26 b, the heat medium is madeto flow because of an air-conditioning load, in the use side heatexchangers 26 c and 26 d there is no air-conditioning load andcorresponding stop valves 24 c and 24 d are closed.

<Cooling-Main Operation>

FIG. 6 is a circuit diagram showing a refrigerant and a heat mediumflows at the time of cooling-main operation. In the cooling-mainoperation, the refrigerant is compressed by the compressor 10, turnedinto a high-temperature high-pressure gas refrigerant to be guided intothe heat source side heat exchanger 12 via the four-way valve 11. There,a gas-state refrigerant is condensed to turn into a two-phaserefrigerant, flows out of the heat source side heat exchanger 12 in thetwo-phase state, flows out of the heat source apparatus 1 via the checkvalve 13 a, and flows into the relay unit 3 via the refrigerant pipeline4. In the relay unit 3, the refrigerant enters the gas-liquid separator14 and a gas refrigerant and a liquid refrigerant in the two-phaserefrigerant are separated into. The gas refrigerant is guided into theintermediate heat exchanger 15 a, condensed and liquefied therein topass through the expansion valve 16 d. Meanwhile, the liquid refrigerantseparated in the gas-liquid separator 14 is flowed to the expansionvalve 16 e, joined with the liquid refrigerant condensed and liquefiedin the intermediate heat exchanger 15 a and passing through theexpansion valve 16 d, and guided to the intermediate heat exchanger 15 bvia the expansion valve 16 a. Then, the refrigerant is expanded by theexpansion valve 16 a to turn into a low-temperature low-pressuretwo-phase refrigerant and the intermediate heat exchanger 15 b operatesas an evaporator. The refrigerant turns into a low-temperaturelow-pressure gas refrigerant in the intermediate heat exchanger 15 b andflows out of the relay unit 3 via the expansion valve 16 c to flow intothe heat source apparatus 1 again via the refrigerant pipeline 4. In theheat source apparatus 1, the refrigerant passes through the check valve13 d to be sucked into the compressor 10 via the four-way valve 11 andthe accumulator 17. Then, the expansion valves 16 b has anopening-degree small enough for the refrigerant not to flow and theexpansion valve 16 c is made to be a full open state so as not to causea pressure loss.

Next, descriptions will be given to movement of the secondary side heatmedium (water, anti-freezing liquid, etc.) In the intermediate heatexchanger 15 a, heating energy of the refrigerant on the primary side istransferred to the heat medium on the secondary side, and the heatedheat medium is made to flow in the secondary side piping by the pump 21a. In the intermediate heat exchanger 15 b, cooling energy of therefrigerant on the primary side is transferred to the heat medium on thesecondary side, and the cooled heat medium is made to flow in thesecondary side piping by the pump 21 b. The heat medium flowed out ofthe pumps 21 a and 21 b passes through the stop valves 24 a to 24 d viathe flow path switching valves 22 a to 22 d to flow into the use sideheat exchangers 26 a to 26 d and the flow amount adjustment valves 25 ato 25 d. Then, through the operation of the flow amount adjustmentvalves 25 a to 25 d, only the heat medium having a flow amount necessaryto cover the air-conditioning load required indoors is made to flow intothe use side heat exchangers 26 a to 26 d, and the remaining passesthrough the bypasses 27 a to 27 d to make no contribution to heatexchange. The heat medium passing through the bypasses 27 a to 27 dmerges with the heat medium passing through the use side heat exchangers26 a to 26 d, and passes through the flow path switching valves 23 a to23 d. The heated heat medium flows into the intermediate heat exchanger15 a to return to the pump 21 a again, and the cooled heat medium flowsinto the intermediate heat exchanger 15 b to return to the pump 21 bagain, respectively. Meanwhile, the heated heat medium and the cooledheat medium are guided to the use side heat exchangers 26 a to 26 dhaving the heating load and the cooling load, respectively, withoutbeing mixed through the operation of the flow path switching valves 22 ato 22 d and 23 a to 23 d. The air-conditioning load required indoors canbe covered by controlling a difference between the detectiontemperatures of the third temperature sensors 33 a to 33 d and thefourth temperature sensors 34 a to 34 d to maintain a target value.

FIG. 6 shows a state in which a heating load is generated in the useside heat exchanger 26 a and a cooling load is generated in the use sideheat exchanger 26 b, respectively.

Since there is no need to flow the heat medium to the use side heatexchanger (including thermo-off) having no air-conditioning load, theflow path is closed by the stop valves 24 a to 24 d and the heat mediumis made not to flow into the use side heat exchanger. In FIG. 6, whilein the use side heat exchangers 26 a and 26 b, the heat medium is madeto flow because of an air-conditioning load, in the use side heatexchangers 26 c and 26 d, there is no air-conditioning load andcorresponding stop valves 24 c and 24 d are closed.

<Heating-Main Operation>

FIG. 7 is a circuit diagram showing a refrigerant and a heat mediumflows at the time of heating-main operation. In the heating-mainoperation, the refrigerant is compressed by the compressor 10, turnsinto a high-temperature high-pressure gas refrigerant, passes throughthe check valve 13 b via the four-way valve 11, and flows out of theheat source apparatus 1 to flow into the relay unit 3 via therefrigerant pipeline 4. In the relay unit 3, the refrigerant isintroduced into the intermediate heat exchanger 15 a through thegas-liquid separator 14, and condensed and liquefied in the intermediateheat exchanger 15 a. Thereafter, the refrigerant passing through theexpansion valve 16 d is branched into flow paths through the expansionvalves 16 a and 16 b. The refrigerant passing through the expansionvalve 16 a is expanded by the expansion valve 16 a to turn into alow-temperature low-pressure two-phase refrigerant and flows into theintermediate heat exchanger 15 b. The intermediate heat exchanger 15 boperates as an evaporator. The refrigerant flowed out of theintermediate heat exchanger 15 b evaporates to turn into a gasrefrigerant and passes through the expansion valve 16 c. On the otherhand, the refrigerant passing through the expansion valve 16 b isexpanded by the expansion valve 16 b to turn into a low-temperaturelow-pressure two-phase refrigerant, and merges with the refrigerantpassing through the intermediate heat exchanger 15 b and the expansionvalve 16 c to turn into a low-temperature low-pressure refrigeranthaving larger dryness. Then, the merged refrigerant flows out of therelay unit 3 to flow into the heat source apparatus 1 again through therefrigerant pipeline 4. In the heat source apparatus 1, the refrigerantpasses through the check valve 13 c to be guided into the heat sourceside heat exchanger 12. The heat source side heat exchanger 12 operatesas an evaporator. Then, the low-temperature low-pressure two-phaserefrigerant is evaporated into a gas refrigerant and sucked into thecompressor 10 via the four-way valve 11 and the accumulator 17. Then,the expansion valve 16 e is made to have a small opening-degree so thatno refrigerant flows.

Next, movement of the secondary side heat medium (water, anti-freezingliquid, etc.) will be explained. In the intermediate heat exchanger 15a, heating energy of the primary side refrigerant is transferred to thesecondary side heat medium and the heated heat medium is made to flow inthe secondary side piping by the pump 21 a. In the intermediate heatexchanger 15 b, cooling energy of the primary side refrigerant istransferred to the secondary side heat medium and the cooled heat mediumis made to flow in the secondary side piping by the pump 21 b. Then, theheat medium flowed out of the pumps 21 a and 21 b passes through thestop valves 24 a to 24 d via the flow path switching valves 22 a to 22 dto flow into the use side heat exchangers 26 a to 26 d and flow amountadjustment valves 25 a to 25 d. Then, through the operation of the flowamount adjustment valves 25 a to 25 d, only the heat medium having aflow amount necessary to cover the air-conditioning load requiredindoors is made to flow into the use side heat exchangers 26 a to 26 d,and the remaining passes through the bypasses 27 a to 27 d to make nocontribution to heat exchange. The heat medium passing through thebypasses 27 a to 27 d merges with the heat medium passing through theuse side heat exchangers 26 a to 26 d, passes through the flow pathswitching valves 23 a to 23 d. The heated heat medium flows into theintermediate heat exchanger 15 a to return to the pump 21 a again, andthe cooled heat medium flows into the intermediate heat exchanger 15 bto return to the pump 21 b again. Meanwhile, the heated heat medium andthe cooled heat medium are guided to the use side heat exchangers 26 ato 26 d having the heating load and the cooling load, respectively,without being mixed through the operation of the flow path switchingvalves 22 a to 22 d and 23 a to 23 d. The air-conditioning load requiredindoors can be covered by controlling a difference between the detectiontemperatures of the third temperature sensors 33 a to 33 d and thefourth temperature sensors 34 a to 34 d to maintain a target value.

FIG. 7 shows a state in which a heating load is generated in the useside heat exchanger 26 a and a cooling load is generated in the use sideheat exchanger 26 b, respectively.

Since there is no need to flow the heat medium to the use side heatexchanger (including thermo-off) having no air-conditioning load, theflow path is closed by the stop valves 24 a to 24 d and the heat mediumis made not to flow into the use side heat exchanger. In FIG. 7, whilein the use side heat exchangers 26 a and 26 b, the heat medium is madeto flow because of an air-conditioning load, in the use side heatexchangers 26 c and 26 d, there is no air-conditioning load andcorresponding stop valves 24 c and 24 d are closed.

As mentioned above, heating operation and cooling operation can befreely performed in each indoor unit 2 by switching the correspondingflow path switching valves 22 a to 22 d and 23 a to 23 d to the flowpath connected to the intermediate heat exchanger 15 a for heating whenheating load is generated in the use side heat exchangers 26 a to 26 d,and by switching the corresponding flow path switching valves 22 a to 22d and 23 a to 23 d to the flow path connected to the intermediate heatexchanger 15 b for cooling when cooling load is generated in the useside heat exchangers 26 a to 26 d.

The flow path switching valves 22 a to 22 d and 23 a to 23 d may be anythat can switch flow paths such as a combination of a three-way valve toswitch three-way flow paths and a stop valve to open/close two-way flowpaths. The flow path switching valve may be configured by a combinationof a stepping-motor-driven mixing valve to change the flow amount ofthree-way flow paths and an electronic expansion valve to change theflow amount of two-way flow paths. In that case, water hammer can beprevented by a sudden opening/closing of the flow path.

The air-conditioning load in the use side heat exchangers 26 a to 26 dis expressed by formula 1 as follows, being obtained by multiplying theflow rate, the density, the constant pressure specific heat of the heatmedium and the difference in temperature of the heat medium at the inletand at the outlet of the use side heat exchangers 26 a to 26 d. Here, Vwdenotes the flow amount of the heat medium, pw the density of the heatmedium, Cpw the constant pressure specific heat of the heat medium, Twthe temperature of the heat medium, suffix “in” the value at the inletof the heat medium of the use side heat exchangers 26 a to 26 d, suffix“out” the value at the outlet of the heat medium of the use side heatexchangers 26 a to 26 d, respectively.

Formula 1

Q=V _(w)*(ρ_(win) *Cp _(win) *T _(win)−ρ_(wout) *Cp _(wout) *T_(wout))˜V _(w)*ρ_(w) *Cp _(w)*(T _(win) −T _(wout))   (1)

When the flow amount of the heat medium flowing to the use side heatexchangers 26 a to 26 d is fixed, the temperature difference of the heatmedium at the inlet and outlet changes according to the change of theair-conditioning load in the use side heat exchangers 26 a to 26 d.Therefore, the temperature difference at the inlet and outlet of the useside heat exchanger 26 a to 26 d is set to be a temporary target and itis possible to flow surplus heat medium to the bypasses 27 a to 27 d tocontrol the flow amount that flows to the use side heat exchangers 26 ato 26 d by controlling the flow amount adjustment valves 25 a to 25 d sothat the temporary target approaches a predetermined target value. Thetarget value of the temperature difference at the inlet and outlet ofthe use side heat exchangers 26 a to 26 d may be set at, for example, 5degrees C. The operation is performed by the controller 300. Detailedexplanations will be given later.

In FIGS. 3 to 7, descriptions are given to the case where the flowamount adjustment valves 25 a to 25 d are a mixing valve installed atthe downstream side of the use side heat exchangers 26 a to 26 d,however, a three-way valve is allowable installed at the upstream sideof the use side heat exchangers 26 a to 26 d.

Then, the heat medium that exchanged heat in the use side heatexchangers 26 a to 26 d and heat medium that passed through bypasses 27a to 27 d with no heat exchange and no change in temperature merge at amerged section thereafter. The following formula (2) holds in the mergedsection. Here, Twin and Twout denote inlet and outlet heat mediumtemperatures of the use side heat exchangers 26 a to 26 d, Vw the flowamount of the heat medium flowing into the flow amount adjustment valves25 a to 25 d, Vwr the flow amount of the heat medium flowing into theuse side heat exchangers 26 a to 26 d, Tw the temperature of the heatmedium after the heat medium flowing through the use side heatexchangers 26 a to 26 d and the heat medium flowing through the bypasses27 a to 27 d are merged.

Formula 2

T _(w)=(V _(wr) /V _(w))*T _(wout)+(1−V _(wr) /V _(w))*T _(win)   (2)

When the heat medium that exchanged heat in the use side heat exchangers26 a to 26 d and the heat medium that passed through the bypasses 27 ato 27 d without heat exchange merge, the temperature difference betweenthe heat media approaches the inlet temperature of the use side heatexchangers 26 a to 26 d by the flow amount that has been bypassed. Forexample, when the total flow amount is 20 L/min, the heat medium inlettemperature of the use side heat exchangers 26 a to 26 d 7 degrees C.,the outlet temperature 13 degrees C., the flow amount flowed toward theuse side heat exchangers 26 a to 26 d side 10 L/min, the temperatureafter merging becomes 10 degrees C. by formula (2).

The heat medium having the temperature after the merging returns fromeach indoor unit to merge and flows into the intermediate heatexchangers 15 a and 15 b. Then, unless the heat exchange amount of theintermediate heat exchanger 15 a or 15 b changes, the temperaturedifference between the inlet and outlet becomes almost the same throughthe heat exchange in the intermediate heat exchangers 15 a or 15 b. Forexample, it is assumed that the temperature difference between the inletand outlet of the intermediate heat exchanger 15 a or 15 b is 6 degreesC., and at first, the inlet temperature of the intermediate heatexchanger 15 a or 15 b is 13 degrees C. and the outlet temperature is 7degrees C. Further, the air-conditioning load in the use side heatexchangers 26 a to 26 d is lowered and the inlet temperature of theintermediate heat exchanger 15 a or 15 b decreases to 10 degrees C.Then, if nothing be done, since the intermediate heat exchanger 15 a or15 b performs heat exchange of almost the same amount, the heat mediumflows out of the intermediate heat exchanger 15 a or 15 b at 4 degreesC. The above is repeated and the temperature of the heat medium rapidlydecreases.

In order to prevent the above, the flow amount of the heat mediumflowing through the use side heat exchanger may be adjusted by changingthe rotation speed of the pumps 21 a and 21 b according to changes inthe air-conditioning load of the use side heat exchangers 26 a to 26 dso that the heat medium outlet temperature of the intermediate heatexchanger 15 a or 15 b approaches a target value. Thereby, when theair-conditioning load is lowered, the rotation speed of the pumpdecreases to achieve energy-saving. When the air-conditioning loadincreases, the rotation speed of the pump increases to cover theair-conditioning load.

The pump 21 operates when cooling load or dehumidifying load occurs inany of the use side heat exchangers 26 a to 26 d, and is stopped whenthere is neither cooling load nor dehumidifying load in any use sideheat exchangers 26 a to 26 d. The pump 21 a operates when the heatingload occurs in any of the use side heat exchangers 26 a to 26 d, and isstopped when there is no heating load in any use side heat exchangers 26a to 26 d.

In the heating only operation and the heating-main operation explainedabove, a low-temperature low-pressure refrigerant flows in the heatsource side heat exchanger 12 and the heat source side heat exchanger 12operates as an evaporator, therefore, a frost formation phenomenonoccurs, in which frost attaches to the circumference of the heat sourceside heat exchanger 12. As the frost formation progresses in the heatsource side heat exchanger 12, an air flow rate is lowered because heatexchange between the refrigerant and the air is disturbed and the airpassage around the heat source side heat exchanger 12 is narrowed.Accordingly, heat exchange amount in the heat source side heat exchanger12 decreases and an evaporation temperature of the refrigerant flowinginside of the heat source side heat exchanger 12 is lowered, causingdeterioration in operation efficiency of the refrigeration cycle. Whenthe frost formation further progresses, closure of air passage finallyoccurs. Therefore, the air-conditioning apparatus is provided with adefrosting operation function to melt the frost surrounding the heatsource side heat exchanger 12. The defrosting operation function isgenerally performed by switching the four-way valve 11 to cooling sideto send the high-temperature high-pressure refrigerant to inside of theheat source side heat exchanger 12. FIG. 8 shows the movement of therefrigerant and the heat medium during the defrosting operation.

At the time of the defrosting operation, the refrigerant behavessimilarly to the cooling only operation. That is, the refrigerant iscompressed by the compressor 10 to turn into a high-temperaturehigh-pressure gas refrigerant and guided to the heat source side heatexchanger 12 via the four-way valve 11. Then, the refrigerant iscondensed and liquefied there, flowed out of the heat source apparatus 1through the check valve 13 a to flow out into the relay unit 3 throughthe refrigerant pipeline 4. In the relay unit 3, the refrigerant entersinto the gas-liquid separator 14 and passes through the expansion valves16 e and 16 a to be guided into the intermediate heat exchanger 15 b.Then, the refrigerant is expanded by the expansion valve 16 a to turninto a low-temperature low-pressure two-phase refrigerant. Theintermediate heat exchanger 15 b operates as an evaporator and therefrigerant turns into a low-temperature low-pressure gas refrigerant.However, in the defrosting operation, unlike the cooling operation,since energy to melt the frost is necessary, the frequency of thecompressor 10 is set at a high frequency to some degree. Therefore,since the refrigerant circulation amount and the cooling load do notmatch, and an excess refrigerant is generated, the opening-degree of theexpansion valve 16 b is controlled and the excess refrigerant isreleased. Then, the refrigerant passing through the expansion valve 16 aand the intermediate heat exchanger 15 b passes through the expansionvalve 16 c, merges with the refrigerant passing through the expansionvalve 16 b, flows out of the relay unit 3, and flows into the heatsource apparatus 1 again through the refrigerant pipeline 4. In the heatsource apparatus 1, the refrigerant passes through the check valve 13 dto be sucked into the compressor 10 via the four-way valve 11 and theaccumulator 17. Then, the expansion valve 16 d is adapted to have asmall opening-degree so as not to flow the refrigerant. The expansionvalve 16 c is made to be a full-open state so as not to generate apressure loss.

A large amount of frost is attached around the heat source side heatexchanger 12, and at the time of melting, the frost releases latent heatat 0 degree C. to turn into water. At the time of defrosting operation,since the refrigerant performs heat exchange in the heat source sideheat exchanger 12 with the frost of 0 degree C., it is cooled up to thetemperature of around 0 degree C. in the heat source side heat exchanger12 to flow out therefrom. Then, since the refrigerant flowed out of theheat source side heat exchanger 12 is cooled up to a temperature atwhich the refrigerant can be fully used as a cooling source, whencooling is required in the use side heat exchangers 26 a to 26 d, therefrigerant is made to circulate therein to be used for cooling.

Since frost formation onto the heat source side heat exchanger 12 occurswhen the ambient temperature is low, there is not necessarily coolingload during the defrosting operation. When no cooling load is available,the expansion valve 16 a is made to have a small opening-degree so thatno refrigerant flows through the expansion valve 16 a and all therefrigerant is made to flow through the expansion valve 16 b.

Next, descriptions will be given to movement of the secondary side heatmedium (water, anti-freezing liquid, and the like). When the coolingload is available, in intermediate heat exchanger 15 b, cooling energyof the refrigerant on the primary side is transferred to the heat mediumon the secondary side, and the cooled heat medium is made to flow in thesecondary side piping by the pump 21 b. The heat medium flowed out ofthe pump 21 b passes through the stop valves 24 a to 24 d via the flowpath switching valves 22 a to 22 d to flow into the use side heatexchangers 26 a to 26 d and the flow amount adjustment valves 25 a to 25d. Then, through the operation of the flow amount adjustment valves 25 ato 25 d, only the heat medium necessary to cover the air-conditioningload required indoors is made to flow into the use side heat exchangers26 a to 26 d, and the remaining passes through the bypasses 27 a to 27 dto make no contribution to heat exchange. The heat medium passingthrough the bypasses 27 a to 27 d merges with the heat medium passingthrough the use side heat exchangers 26 a to 26 d, passes through theflow path switching valves 23 a to 23 d, and flows into the intermediateheat exchanger 15 b to be sucked again into the pump 21 b. Theair-conditioning load required indoors can be covered by controlling theflow amount adjustment valves 25 a to 25 d so as to keep the differencein temperature between the use side heat exchanger inlet temperatures 33a to 33 d and use side heat exchanger outlet temperatures 34 a to 34 dto be a target value.

When the heating load is available, the heat medium in the flow pathpassing through the intermediate heat exchanger 15 a is heated to, forexample 50 degrees C. by the heating operation prior to the defrostingoperation. Then, the heated heat medium is made to flow in the secondaryside piping by the pump 21 a. The heat medium flowed out of the pump 21a passes through the stop valves 24 a to 24 d via the flow pathswitching valves 22 a to 22 d to flow into the use side heat exchangers26 a to 26 d and the flow amount adjustment valves 25 a to 25 d. Then,through the operation of the flow amount adjustment valves 25 a to 25 d,only the heat medium necessary to cover the heating load requiredindoors is made to flow into the use side heat exchangers 26 a to 26 d,and the remaining passes through the bypasses 27 a to 27 d to make nocontribution to heat exchange. The heat medium passing through thebypasses 27 a to 27 d merges with the heat medium passing through theuse side heat exchangers 26 a to 26 d, passes through the flow pathswitching valves 23 a to 23 d, and flows into the intermediate heatexchanger 15 a to be sucked again into the pump 21 b. Theair-conditioning load required indoors can be covered by controlling thedifference in temperature between the third temperature sensors 33 a to33 d and the fourth temperature sensors 34 a to 34 d to maintain apredetermined target value.

During the defrosting operation, in the intermediate heat exchanger 15a, because heating energy is not supplied from the refrigerant, thetemperature of the heat medium is lowered by as much as the heating loadin the use side heat exchangers 26 a to 26 d. However, with theabove-mentioned heating function during the defrosting operation beingprovided, the heating operation can be continued as long as thetemperature of the heat medium is equal to or higher than a certaintemperature to some degree, for example, 35 degrees C. Regarding theheating operation function during the defrosting operation, descriptionswill be given to concrete examples.

For example, it is assumed that the temperature of the heat medium is 50degrees C. at the start of the defrosting operation, and it is possibleto perform the heating operation when equal to or higher than 35 degreesC. The flow amount of the heat medium is assumed to be 20 L per minutefor each use side heat exchanger 26 a to 26 d. The heating load in theuse side heat exchangers 26 a to 26 d is made to be a value that canjust be covered by making the temperature difference of the heat mediumat the outlet and inlet of each use side heat exchanger 26 a to 26 d tobe 5 degrees C. During the heating operation prior to the start ofdefrosting, heat amount is assumed to have been supplied that can give 5degrees C. temperature difference at the outlet and inlet of theintermediate heat exchanger 15 a under the above conditions. The pipingin which the heat medium circulates is assumed to have a length for therefrigerant to take a round in one minute. When the defrosting operationstarts under these conditions, there will be no heating amount in theintermediate heat exchanger 15 a, therefore, the outlet temperature ofthe intermediate heat exchanger 15 a decreases 5 degrees C. in oneminute. Accordingly, it is possible to continue heating operation untilthe heat medium whose initial temperature is 50 degrees C. becomes 35degrees C., that is, until the temperature of the heat medium drops by15 degrees C., therefore, heating operation can be continued for threeminutes in total. Usually, three minutes is enough to complete thedefrosting operation. That is, it is possible to cover heating duringthe defrosting operation only by the circulation of the refrigerant onthe secondary side. Even if the defrosting operation is furtherextended, the time in which heating energy can not be supplied toindoors is the time obtained by subtracting the time in which heating isperformed only by circulation of the heat medium from the time of thedefrosting operation. Therefore, decrease in the room temperature can bedrastically made small during the time of the defrosting operation.

When needing to continue heating longer even if the heating capacity islowered a little, the flow amount of the heat medium has only to belowered by decreasing the rotation speed of the pump 21 a to less thanthe operation condition prior to the start of the defrosting operation.For example, if the rotation speed is halved of the time when thedefrosting operation started, heating operation can be continued fortwice the time. Thus, time to stop the heating operation during thedefrosting operation can be shortened, improving the comfort of indoorscompared with the case of no heating operation.

When the detection temperature of at least either a first temperaturesensor 31 a or a second temperature sensor 32 a that detects thetemperature of the entrance or the exit of the intermediate heatexchanger 15 a becomes equal to or lower than a predetermined settemperature, the pump 21 a may reduce the operation capacity or stop theoperation. The above-mentioned set temperature is a lower limittemperature (a heating limit temperature) at which heating operation ispossible, therefore, it may be suitably determined, for example, may be30 to 35 degrees C. The control may be performed by installing atemperature sensor at the inlet side or the outlet side of the pump 21 ato utilize the detected temperature.

In addition, it is conceivable that during the defrosting operation, theuse side heat exchanger in operation undergoes thermo-off to stop orundergoes thermo-on to start. Therefore, in order to make the load to becorresponded more appropriately, a discharge capacity of the pump 21 amay be determined according to the required heating capacity of the useside heat exchanger at that time. The required heating capacity of theuse side heat exchanger can be calculated by installing a flow meterthat measures the flow amount of the heat medium flowing through the useside heat exchanger and measuring the flow amount of the heat mediumbased on the above-mentioned formula (1). It may be determined based ona capacity code representing the heat exchange capacity of each use sideheat exchanger. Further, when the capacity of each use side heatexchanger does not differ so much from each other, it may be determinedroughly by the number of units in operation of the use side heatexchangers.

During the defrosting operation, since there is no need to flow the heatmedium to the use side heat exchanger (including thermo-off) having noair-conditioning load, the flow path is closed by the stop valves 24 ato 24 d so as not to flow the heat medium to the use side heatexchanger. FIG. 8 shows a case where the use side heat exchanger 26 ahas a heating load and the use side heat exchanger 26 b has a coolingload, and the use side heat exchangers 26 c and 26 d have noair-conditioning load and the corresponding stop valves 24 c and 24 dare closed.

Next, descriptions will be given to the flow amount control operation ofthe heat medium by the controller 300 based on the flow chart of FIG. 9.Here, it will be explained the flow path switching valves 22 a to 22 das a flow path switching valve 22 and with the flow path switchingvalves 23 a to 23 d being the flow path switching valve 23.

When the controller starts processing (ST0), the presence/absence of theindoor unit is determined (ST1, ST3) that performs cooling (ordehumidifying) operation or heating operation. When there is an indoorunit that performs cooling (or dehumidifying) operation, the pump 21 bon the cooling side is operated (ST2). When there is an indoor unit thatperforms heating, the temperature of the heat medium is checked to beequal to or higher than a predetermined heating limit temperature (s4)and the pump 21 a on the heating side is operated (ST5) Then, regardingthe relevant indoor units, states of all the indoor units are checkedfrom number 1 in order (ST7, ST16, ST17). The “n” in the figure denotesa number of the indoor unit. When the indoor unit performs heatingoperation (ST8), the flow path switching valves 22 and 23 correspondingto the indoor unit are switched to the intermediate heat exchanger 15 afor heating (ST9), the detection temperature T1 of the third temperaturesensors 33 a to 33 d and the detection temperature T2 of the fourthtemperature sensors 34 a to 34 d are obtained, and the value obtained bysubtracting T2 from T1 is set to be a Δ Tr (ST10). On the other hand,when the indoor unit performs cooling operation, the flow path switchingvalves 22 and 23 corresponding to the indoor unit are switched to theintermediate heat exchanger 15 b for cooling (ST11), the detectiontemperature T1 of the third temperature sensors 33 a to 33 d and thedetection temperature T2 of the fourth temperature sensors 34 a to 34 dare obtained, and the value obtained by subtracting T1 from T2 is set tobe a Δ Tr (ST12). When the difference in temperature between a controltarget value Tmr and Δ Tr is larger than a safety region Trs,opening-degree (opening area) of the corresponding flow amountadjustment valves 25 a to 25 d is reduced (ST13, ST14), and when thedifference in temperature between the control target value Tmr and Δ Tris smaller than a safe region Trs, the opening-degree (opening area) ofthe corresponding flow amount adjustment valves 25 a to 25 d isincreased (ST13, ST15). Δ Tr is controlled to come closer to the controltarget value and each heating load and cooling load is covered.

Trs may be set at 0 degree C. and no safety region may be provided.However, when the safety region is provided, the number of controllingthe flow amount adjustment valves 25 a to 25 d is reduced and a valvelife will be prolonged.

During the defrosting operation, cooling energy is supplied from therefrigerant to the intermediate heat exchanger 15 b, however, heatingenergy is not supplied from the refrigerant to the intermediate heatexchanger 15 a. Therefore, when the detection temperature of the firsttemperature sensor 31 a at the inlet of the pump 21 a becomes lower thana set heating limit temperature Td1, for example 35 degrees C., the pump21 a is stopped (ST4, ST6). When the pump 21 a is stopped, heatingoperation is stopped, as well. In place of stopping the pump 21 a, itsoperation capacity may be reduced.

These procedures are repeated for each predetermined time period. Here,in the case of the control target being 5 degrees C. and safety regionbeing 1 degree C., for example, when the temperature difference betweenthe inlet and outlet of the use side heat exchanger Δ Tr is 3 degreesC., the opening-degree (opening area) of the flow amount adjustmentvalves 25 a to 25 d are controlled so that the flow amount flowingthrough the use side heat exchangers 26 a to 26 d is reduced. On theother hand, if the temperature difference between the inlet and outletof the use side heat exchanger Δ Tr is 7 degrees C., the opening-degree(opening area) of the flow amount adjustment valves 25 a to 25 d arecontrolled so that the flow amount flowing through the use side heatexchangers 26 a to 26 d increases. Then, through the above-mentionedoperations, the temperature difference between the inlet and outlet ofthe use side heat exchanger Δ Tr is made to approach the control target.During the heating operation, when the inlet or the outlet temperatureof the pump 21 a is 45 degrees C. at the time of the start of heating,if the temperature turns into a predetermined heating limit temperature,35 degrees C. for example, the pump 21 a is made to be stopped or itsoperation capacity is decreased.

The heating limit temperature for stopping the heating operation by thecirculation of the heat medium during the defrosting operation can bedetected by using any of the detection temperature of the firsttemperature sensor 31 a, the second temperature sensor 32 a, the thirdtemperature sensors 33 a to 33 d, and the fourth temperature sensors 34a to 34 d, in addition to the inlet or outlet temperature of the pump 21a. However, since the detection temperature of the fourth temperaturesensors 34 a to 34 d changes according to the control, it is morepreferable to use the other three detection temperatures.

Embodiment 2

FIG. 10 is a circuit diagram for the refrigerant and the heat medium ofthe air-conditioning apparatus according to Embodiment 2 of the presentinvention. The air-conditioning apparatus according to Embodiment 2 isthe same as that of Embodiment 1 except that a two-way flow amountadjustment valve is employed as the flow amount adjustment valves 25 ato 25 d and that the stop valves 24 a to 24 d are omitted. The two-wayflow amount adjustment valve is employed that can continuously changethe opening-degree using a stepping motor and the like. Control of thetwo-way flow amount adjustment valve is similar to the case of thethree-way flow amount adjustment valve. By adjusting the opening-degreeof the two-way flow amount adjustment valve, the flow amount flowed intothe use side heat exchangers 26 a to 26 d is controlled such that thetemperature difference between before and after the use side heatexchangers 26 a to 26 d becomes 5 degrees C., for example. Thereafter,the rotation speed of the pumps 21 a and 21 b is controlled so that thetemperature of the inlet side or the outlet side of the intermediateheat exchangers 15 a and 15 b becomes the target value. When employingthe two-way flow amount adjustment valve as the flow amount adjustmentvalves 25 a to 25 d, since it can be used for opening and closing theflow path, the stop valves 24 a to 24 d become unnecessary, yielding amerit that the system can be constructed at low cost.

In Embodiments 1 and 2, descriptions are given to the case where boththe first temperature sensors 31 a and 31 b and the second temperaturesensors 32 a and 32 b are installed, however, in order to control thepumps 21 a and 21 b, either of the first temperature sensors 31 a and 31b or the second temperature sensors 32 a and 32 b may be enough. Duringthe defrosting operation, since heating energy is not supplied with theintermediate heat exchanger 15 a, the heat medium inlet temperature andthe heat medium outlet temperature of the intermediate heat exchanger 15a becomes almost the same.

As for the refrigerant, a single refrigerant such as R-22 and R-134a,pseudo-azeotropic mixture refrigerant such as R-410A and R-404A,azeotropic mixture refrigerant such as R-407C, the refrigerant or itsmixture that is regarded to have a smaller global warming potential suchas CF₃CF═CH₂ including a double bond in the chemical formula, or anatural refrigerant such as CO₂ and propane, can be utilized.

The refrigerant circuit is configured to contain an accumulator 17,however, the present invention is effective without it. Descriptions aregiven to the case where there are the check valves 13 a to 13 d,however, these are not indispensable for the present invention. Withoutthem, the present invention can be constituted and its working effectcan be achieved.

A fan should be attached to the heat source side heat exchanger 12 andthe use side heat exchangers 26 a to 26 d and it is preferable topromote condensation and evaporation by blowing. It is not limitedthereto, however, but as for the use side heat exchangers 26 a to 26 d,a panel heater utilizing radiation may be employed. As for the heatsource side heat exchanger 12, a water-cooled type may be employed thatmoves heat by water and anti-freezing liquid. Any type is allowablehaving a structure that can release or absorb heat.

Descriptions are given to the case where there are four use side heatexchangers 26 a to 26 d, however, at least one may be allowable for thepresent invention. There is no limit for the number of units.

Descriptions are given to the case where the flow path switching valves22 a to 22 d and 23 a to 23 d, the stop valves 24 a to 24 d, and theflow amount adjustment valves 25 a to 25 d are connected with the useside heat exchangers 26 a to 26 d on a one-by-one basis, however, it isnot limited thereto. Each use side heat exchanger may be connected witha plurality of them. Thereby, the plurality of them connected to thesame use side heat exchanger may be operated in the same way.

Descriptions are given to the case where there are two intermediate heatexchangers 15 a and 15 b, however, it is not limited thereto. The numberof the intermediate heat exchanger can be increased according to thenumber of indoor units.

Descriptions are given to the case where the flow amount adjustmentvalves 25 a to 25 d, the third temperature sensors 33 a to 33 d, and thefourth temperature sensors 34 a to 34 d are installed in the relay unit3, however, it is not limited thereto. The same operation and effect maybe obtained by installing them inside or near the indoor unit 2. Whenemploying a two-way flow amount adjustment valve for the flow amountadjustment valves 25 a to 25 d, the third temperature sensors 33 a to 33d and the fourth temperature sensors 34 a to 34 d may be installedinside or near the relay unit 3, and the flow amount adjustment valves25 a to 25 d may be installed inside or near the indoor unit 2.

The air-conditioning apparatus according to the present embodimentexplained above can cover the heating load by circulating the warm heatmedium on the secondary side during the defrost operation to suppressthe lowering of the room temperature. By allowing the relay unit 3 to beseparately formed from the use side heat exchangers 26 a to 26 d and theheat source side heat exchanger 12 and installed at a separate positionfrom each other, the pump power can be made small for transferring theheat medium so as to improve the system efficiency including defrosting.Accordingly, operation having high energy-saving property can beperformed.

1. An air-conditioning apparatus, comprising: at least one intermediateheat exchanger exchanges heat between a refrigerant and the heat mediumdifferent from said refrigerant; a refrigerating cycle in which acompressor, a heat source side heat exchanger, at least one expansionvalve, and a refrigerant side flow path of said intermediate heatexchanger are connected via piping through which said refrigerant flows;and a heat medium circulation circuit in which a heat medium side flowpath of said intermediate heat exchanger, a pump, and a use side heatexchanger are connected via piping through which said heat medium flows;wherein said heat source side heat exchanger, said intermediate heatexchanger, and said use side heat exchanger are formed in a separatebody, there is provided a defrosting operation function that introducesa high temperature and high pressure refrigerant into said heat sourceside heat exchanger by operating said compressor and melts the frostattached around said heat source side heat exchanger, and whileperforming said defrosting operation function said pump is operatedwithout flowing said refrigerant through said intermediate heatexchanger for heating, the heat medium having heating energy in saidintermediate heat exchanger for heating and heat medium circulationcircuit including the same is made to circulate between said use sideheat exchanger in need of heating and said intermediate heat exchanger.2. (canceled)
 3. The air-conditioning apparatus of claim 1, wherein aplurality of units of said use side heat exchangers are made to beconnectable in parallel with each intermediate heat exchanger, andoperation capacity of said pump is determined according to a total ofcapacity code of said use side heat exchanger performing heatingoperation, a total of units, or a total value of required heatingcapacity.
 4. The air-conditioning apparatus of claim 1, wherein a flowamount adjustment valve is disposed that adjusts a flow amount of a heatmedium at an inlet side flow path or an outlet side flow path of saiduse side heat exchanger, temperature sensors are disposed that detect atemperature of the heat medium flowing into said use side heat exchangerand a temperature of the heat medium flowing out from said use side heatexchanger, and the flow amount of said flow amount adjustment valve isadjusted so that a difference between the detection temperatures of saidtemperature sensors is made to approach a predetermined target value. 5.The air-conditioning apparatus of claim 3, wherein when a detectiontemperature of at least either of said temperature sensors becomes equalto or lower than a predetermined heating limit temperature, said pump ismade to decrease operation capacity or made to stop operation.
 6. Theair-conditioning apparatus of claim 1, wherein temperature sensors aredisposed that detect a temperature of a heat medium at the inlet side orthe outlet side of said intermediate heat exchanger or at the inlet sideor the outlet side of said pump, and when the detection temperature ofany of the temperature sensors becomes equal to or lower than apredetermined heating limit temperature, said pump is made to decreaseoperation capacity or made to stop operation.
 7. The air-conditioningapparatus of claim 1, wherein the operation capacity of said pump at thedefrosting operation is set at a smaller value than the operationcapacity prior to the defrosting operation.
 8. The air-conditioningapparatus of claim 1, wherein said intermediate heat exchanger isinstalled outside of the space subjected to air-conditioning of said useside heat exchanger.